For most of baseball history, active rosters expanded from 25 to the full 40 on September 1. Since 2020 the limit has been 28, with a cap of 14 pitchers. The change was deliberate, and the reasons come down to three complaints that had built up for decades.
Reason One: September Wasn’t the Same Sport
The core objection was that the final month of the regular season was played under different rules from the first five. A pennant race decided in September was decided by teams operating with rosters half again as large as the ones that got them there.
Nothing else in professional sport works that way. The games that mattered most were played under the least representative conditions.
Reason Two: Bullpen Parades
With unlimited pitchers available, September games turned into relay races. A manager could use a different arm for every batter in a late inning, and did.
The consequence was games that ran materially longer in September than in June, at exactly the point in the calendar when the sport most wanted new viewers. Pace of play was already the league’s central preoccupation, and expanded rosters cut directly against it. The 14-pitcher cap exists specifically to stop this.
Reason Three: It Wasn’t Fair
Teams did not expand equally. A club with organisational depth and money could call up a dozen players; a smaller-payroll club with a thinner 40-man might add three or four.
So two teams fighting for the same wild card spot could go into a head-to-head series with meaningfully different bench and bullpen sizes. That is a competitive imbalance created by roster rules rather than by baseball, and it was the argument that carried most weight with the union and the league alike.
What the New Rule Actually Says
| Old system | Now | |
|---|---|---|
| Roster before Sept. 1 | 25 | 26 |
| Roster from Sept. 1 | Up to 40 | 28 |
| Pitcher limit | None | 13, rising to 14 in September |
| Every spot filled? | Optional — teams chose how many to add | Mandatory — all 28 must be filled |
That last line is often missed. Under the old rules a club could decline to expand at all. Now the 28 spots are compulsory, which is itself a fairness measure — nobody can gain an edge by carrying fewer players.
What Was Lost
The romance, mostly. September used to be when a fan of a losing team got a first look at the next wave — a dozen unfamiliar names, a few of whom would matter in three years. That has largely moved to June and July, when prospects now debut.
Journeyman minor leaguers also lost something concrete. A September call-up was often the only major league service a career minor leaguer would ever get, and there are far fewer of those cups of coffee now.
The Bottom Line
MLB scrapped 40-man September rosters because the final month was being played under different rules from the rest of the season, because unlimited pitching changes were lengthening games, and because clubs with more depth gained an advantage that had nothing to do with baseball. Rosters now go to 28 with a 14-pitcher cap, and all 28 spots must be filled. Our September call-ups explainer covers how the current system works.